President Trump’s war of words with North Korea has raised doubts in the minds of US senators that the president would listen to advisers trying to talk him out of launching a nuclear attack.

The US Senate has openly discussed the president's nuclear authority for the first time in more than 40 years, prodded by aggressive comments made by President Donald Trump about North Korea.

Among the questions asked was whether Trump has the sole authority to order nuclear attacks without any controls in place.

Some pointed out that the decision is usually a consultative process where the US president is advised by senior figures in government.

The fear seems to be, as voiced by Senator Markey, that Trump would refuse to take advice offered and that the current power structures in Washington would render those around him incapable of dissuading him from a decision to attack.